Silicone matrix-type

CombiPatch is a three- or four-day patch that delivers both estradiol and norethin-drone acetate. CombiPatch is available in two sizes a 9-cm2 patch that delivers 0.05 mg of estradiol per day and 0.14 mg of norethindrone acetate per day and a 16-cm2 patch that delivers 0.05 mg of estradiol per day and 0.25 mg of norethindrone acetate per day. Estradiol is a lipophilic compound with a molecular weight of 272. The molecular weight of norethindrone acetate is 340. The design of the patch is considered an adhesive-matrix-type patch that consists of three layers. The backing is comprised of polyolefin and the adhesive layer contains a silicone adhesive, acrylate adhesive, estradiol, norethindrone acetate, oleic acid, and oleyl alcohol. 

For the purpose of composition optimization of the silicone matrix, two types (1, II) of polyaddition compounds were researched. Special additional agents (QM) were synthesized for increasing tensile strength. 

These foams can be defined as composites consisting of hollow microspheres and a polymeric matrix. This one is made of a thermosetting (PU, PIR, PF, EP, silicone or unsaturated polyester) or of a thermoplastic (PE, PP, PVC, PS, polyimide) [56]. The microspheres can be made of silica, glass, carbon, ceramics or polymers such as PS, PE, PP, polyamide (PA), polymethyl methacrylate (PMMA), divinyl benzene (DVB)-maleic anhydride, and so on [56-58]. The diameter of the tiny hollow spheres is 300 mm or less [35]. They contain an inert gas such as nitrogen or a CFC. The properties of these syntactic foams depend on matrix type, microsphere type (and the contained gas), ratio matrix to microspheres, curing process, production technology. Syntactic foams can be made in combination with the conventional ones. Such a complex composite can be formnlated into a mouldable mass then shaped or pressed into cavities. 

Square lattice with silicon pillars or airholes in silicon matrix (proton beam writing + electrochemical etching on p-type Si wafer)... 

Vulcanization kinetics of the composites vulcanization are very similar regardless refractory filler type, excluding the mix containing surface modified montmorillonite (M-MMT) (Table 8.2). In its case values of torque were significantly lower than for other samples minimum (M j ), optimum (M ) and maximum (M ) torque values, respectively, from 14 to 27%, from 34 to 40% and from 35 to 41%. This effect can by explained by plasticization of silicone matrix by quaternary ammonium salt present in M-MMT. Also values of scorch (tp2) and vulcanization (t ) time... 

Transdermal drug-delivery systems offer several important adventages over more traditional approaches, in addition to the benefits of avoiding the hepatic first-pass effect. Transdermal drug delivery systems (TDDS) are usually in the form of patches incorporating pressure sensitive adhesives. There are two basic designs for transdermal patches matrix or reservoir type. Matrix-type patches include monolithic adhesive and polymer matrices, whereas reservoir-type patches include liquid and solid-state reservoirs [71-73]. For various types of transdermal delivery systems, medical grade adhesive silicones are used as [73,74] ... 

A third type of silicone implant fabrication is a hybrid of the capsule and matrix-type implants such as microsealed drug delivery system." This system consists of a matrix-type silicone im.plant with microsealed compartments containing drug/steroid dissolved or suspended in a hydrophilic solvent. Addition of solvents in the silicone implants changes the physical structure of the silicone network and affects the solubility and diffusivity of drugs/hormones so that release fluxes of drugs/hormones increase."... 

The most common type of silicone implant used by the biologist is the capsule-type implant whereas the matrix-type of implant is the most frequently employed for commercial products. One reason for this difference is that when a crystalline compound is placed in a capsule it is quite evident after it has been used whether it can be used for further experimentation. However, upon implantation caution must be taken to avoid puncture of the capsule membrane which causes a larger than desired release of the drug/hormone. Less damage is done to matrix-type implants due to punctures. 

Phosphoric Acid Fuel Cell This type of fuel cell was developed in response to the industiy s desire to expand the natural-gas market. The electrolyte is 93 to 98 percent phosphoric acid contained in a matrix of silicon carbide. The electrodes consist of finely divided platinum or platinum alloys supported on carbon black and bonded with PTFE latex. The latter provides enough hydrophobicity to the electrodes to prevent flooding of the structure by the electrolyte. The carbon support of the air elec trode is specially formulated for oxidation resistance at 473 K (392°F) in air and positive potentials. 

The heart of the energy-dispersive spectrometer is a diode made from a silicon crystal with lithium atoms diffiised, or drifted, from one end into the matrix. The lithium atoms are used to compensate the relatively low concentration of grown-in impurity atoms by neutralizing them. In the diffusion process, the central core of the silicon will become intrinsic, but the end away from the lithium will remain p-type and the lithium end will be n-type. The result is a p-i-n diode. (Both lithium-... 

Liquid membranes in this type of ion-selective electrodes are usually heterogeneous systems consisting of a plastic film (polyvinyl chloride, silicon rubber, etc.), whose matrix contains an ion-exchanger solution as a plasticizer (see Fig. 6.5). 

These incorporate membranes fabricated from insoluble crystalline materials. They can be in the form of a single crystal, a compressed disc of micro-crystalline material or an agglomerate of micro-crystals embedded in a silicone rubber or paraffin matrix which is moulded in the form of a thin disc. The materials used are highly insoluble salts such as lanthanum fluoride, barium sulphate, silver halides and metal sulphides. These types of membrane show a selective and Nemstian response to solutions containing either the cation or the anion of the salt used. Factors to be considered in the fabrication of a suitable membrane include solubility, mechanical strength, conductivity and resistance to abrasion or corrosion. 

In practice, three types of membrane based on silver halides are used. The oldest type is based on silver halide precipitate in a matrix of silicone rubber. 

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